The 'achievability frontier' describing the trade-off between maximum 21st century surface air temperature increase and aggregated mitigation costs for the <em>Frag2015</em> scenario with <em>default</em> technology assumptions

<p><strong>Figure 1.</strong> The 'achievability frontier' describing the trade-off between maximum 21st century surface air temperature increase and aggregated mitigation costs for the <em>Frag2015</em> scenario with <em>default</em> technology assumptions. Shaded bands show uncertainty ranges of the climate system's response to anthropogenic activities.</p> <p><strong>Abstract</strong></p> <p>While the international community aims to limit global warming to below 2 ° C to prevent dangerous climate change, little progress has been made towards a global climate agreement to implement the emissions reductions required to reach this target. We use an integrated energy–economy–climate modeling system to examine how a further delay of cooperative action and technology availability affect climate mitigation challenges. With comprehensive emissions reductions starting after 2015 and full technology availability we estimate that maximum 21st century warming may still be limited below 2 ° C with a likely probability and at moderate economic impacts. Achievable temperature targets rise by up to ~0.4 ° C if the implementation of comprehensive climate policies is delayed by another 15 years, chiefly because of transitional economic impacts. If carbon capture and storage (CCS) is unavailable, the lower limit of achievable targets rises by up to ~0.3 ° C. Our results show that progress in international climate negotiations within this decade is imperative to keep the 2 ° C target within reach.</p>